Method for the improved oxidation of secondary amine groups

ABSTRACT

The present invention relates to a process for oxidizing secondary amino groups to the corresponding radical nitroxyl groups within a polymer comprising, for example, 2,2,6,6-tetramethylpiperidinyl units. The process assures a particularly high degree of oxidation.

The present invention relates to a process for oxidizing secondary amino groups to the corresponding radical nitroxyl groups within a polymer comprising, for example, 2,2,6,6-tetramethylpiperidinyl units. The process assures a particularly high degree of oxidation.

BACKGROUND OF THE INVENTION

Organic batteries are electrochemical cells which use an organic charge storage material as active electrode material for storing electrical charge. These secondary batteries are notable for their exceptional properties, such as fast chargeability, long lifetime, low weight, high flexibility and ease of processibility. Active electrode materials for charge storage which have been described in the prior art are various polymeric structures, for example polymeric compounds having organic nitroxyl radicals as active units (for example in WO 2012/133202 A1, WO 2012/133204 A1, WO 2012/120929 A1, WO 2012/153866 A1, WO 2012/153865 A1 JP 2012-221574 A, JP 2012-221575 A, JP 2012-219109 A, JP 2012-079639 A, WO 2012/029556 A1, WO 2012/153865 A1, JP 2011-252106 A, JP 2011-074317 A, JP 2011-165433 A, WO 2011034117 A1 WO 2010/140512 A1, WO 2010/104002 A1, JP 2010-238403 A, JP 2010-163551 A, JP 2010-114042 A, WO 2010/002002 A1, WO 2009/038125 A1, JP 2009-298873 A, WO 2004/077593 A1, WO 2009/145225 A1, JP 2009-238612 A, JP 2009-230951 A, JP 2009-205918 A, JP 2008-234909 A, JP 2008-218326 A, WO 2008/099557 A1, WO 2007/141913 A1, US 2002/0041995 A1, EP 1128453 A2; A. Vlad, J. Rolland, G. Hauffman, B. Ernould, J.-F. Gohy, CherriSusChem 2015, 8, 1692-1696) or polymeric compounds having organic phenoxyl radicals or galvinoxyl radicals as active units (for example US 2002/0041995 A1, JP 2002-117852 A).

Particular emphasis should be given here to poly(2,2,6,6-tetramethylpiperidinyloxylmethacrylate), the synthesis of which is described by K. Nakahara, S. Iwasa, M. Satoh, Y. Morioka, J. Iriyarna, M. Suguro, E. Hasegawa, Chem Phys Lett 2002, 359, 351-354 and J. Kim, G. Cheruvally, J. Choi, J. Ahn, S. Lee, S. Choi, C. Song, Solid State Ionics 2007, 178, 1546-1551. Further synthesis methods are described in the following publications; JP 2006-022177 A, WO 2015/032951 A1, EP 1 752 474 A1, EP 1 911 775 A1, EP 2 042 523 A1. Moreover, Liang Wenzhong also describes, in Polymer Degradation and Stability 1991, 31, 353-364, nitroxidation to form this polymer, wherein the solvent used is ethanol in excess.

Particular emphasis should be given to EP 1 911 775 A1, which describes a process for polymerizing 2,2,6,6-tetramethylpiperidinyl methacrylate and subsequently oxidizing the secondary amino groups within the 2,2,6,6-tetramethylpiperidinyl unit to give a radical 2,2,6,6-tetramethylpiperidinyloxyl group (“nitroxylation” hereinafter). The nitroxylation level (or oxidation level) achieved in this prior art document is high at 95.5%. There is nevertheless still a need to achieve an even better degree of oxidation.

In addition, EP 1 911 775 A1 states in paragraph [0046] that the process is applicable within a wide temperature range of 0 to 90° C. Nevertheless, it is apparent from the example of EP 1 911 775 A1 described in paragraphs [0053], [0054] and [0055] that the polymerization should best be conducted at high temperatures such as 80° C.

However, performance at such a high temperature is economically disadvantageous. On the industrial scale in particular, it is desirable to be able to conduct of this reaction without having to expend additional energy for heating of the reaction solution. In some cases, it is additionally also desirable to be able to conduct the reaction with cooling below 0° C., since the cooling allows better control over the occurrence of significant exotherms.

The problem addressed by the present invention is therefore that of providing a process which achieves maximum oxidation of the secondary amino groups in a polymer comprising 2,2,6,6-tetramethylpiperidinyl groups or similar groups to radical nitroxyl groups. The process should lead to better oxidation rates, specifically also at room temperature and lower temperatures.

A process which solves the aforementioned problem has now surprisingly been found.

DETAILED DESCRIPTION OF THE INVENTION

1) The present invention accordingly relates to processes for preparing a polymer P¹ comprising n¹ repeat units of the general chemical structure (I)

which is characterized in that a polymer P² comprising n² repeat units of the general chemical structure (II)

is oxidized in a solvent comprising water and ethanol, where the ethanol is present in the solvent n deficiency relative to water, especially at a temperature T₁≤40° C.,

where n¹, n² are each independently an integer in the range of 4-3 000 000, especially 4-1 000 000, preferably 4-100 000, more preferably 4-10 000, even more preferably 4-5000,

where the repeat units of the chemical structure (I) within the polymer P¹ are the same or at least partly different from one another,

where the repeat units of the chemical structure (I) within the polymer P¹ are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

where the repeat units of the chemical structure (II) within the polymer P² are the same or at least partly different from one another,

where the repeat units of the chemical structure (II) within the polymer P² are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

and where, in the chemical structures (I) and (II), the R¹, R², R³, R⁴, R⁵ radicals are selected from the group consisting of hydrogen, branched or unbranched alkyl group having 1 to 4 carbon atoms, preferably R¹, R², R³, R⁴=methyl and R⁵=hydrogen or methyl,

X is selected from the group consisting of *—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, *—C═CH—**,

where “*” in each case denotes the bond to the carbon atom joined to R¹ and R²,

where “w*” in each case denotes the bond to the carbon atom joined to R³ and R⁴,

where “C′” denotes a carbon atom additionally joined to the Y radical,

where Y is selected from the bridging radicals (III) and (IV),

-   -   where (III) has the structure &-(Y¹)_(p1)         [C═X¹]_(p2)—(Y²)_(p3)—B—(Y³)_(p6)—[C═X²]_(p5)—(Y⁴)_(p4)—&&,     -   and where (IV) has the structure         &-(Y⁵)_(p9)—(C═X³)_(p8)—(Y⁶)_(p7)-&&,     -   where, in the bridging radicals (III) and (IV),     -   p1, p2, p3 are each 0 or 1, with the proviso that it is not         simultaneously the case that p1=p3=1 and p2=0,     -   p4, p5, p6 are each 0 or 1, with the proviso that it is not         simultaneously the case that p4=p6=1 and p5=0,     -   p7, p8, p9 are each 0 or 1, with the proviso that it is not         simultaneously the case that p7=p9=1 and p8=0, and that, when         p7=1 and p8=0, p9=0,     -   X¹, X², X³ are independently selected from the group consisting         of O, S,     -   Y¹, Y², Y³, Y⁴, Y⁵, Y⁶ are independently selected from the group         consisting of O, S, NH, N-alkyl,     -   and where Y¹, when p1=1, p2=p3=0, may also be N O.,     -   and where Y⁴, when p4=1, p5=p6=0, may also be N O.,     -   and where Y⁵, when p9=1, p7=p8=0, may also be N O.,     -   B is a divalent, optionally substituted (hetero)aromatic radical         or a divalent, optionally substituted aliphatic radical, where         the optionally substituted aliphatic radical may additionally         have at least one group selected from ether, thioether,         optionally nitroxylated amino ether, carbonyl group, carboxylic         ester group, carboxamide group, sulphonic ester group,         phosphoric ester,

and where “&&” for Y denotes the bond via which Y is joined to X and where “&” for Y denotes the bond via which Y is joined to the carbon atom joined to R⁵.

2) In a particular embodiment of the present invention, the invention relates to a process for preparing a polymer P¹ comprising n¹ repeat units of the general chemical structure (I)

which is characterized in that a polymer P² comprising n² repeat units of the general chemical structure (II)

is oxidized in a solvent comprising water and ethanol, where the ethanol is present in the solvent in deficiency relative to water, especially at a temperature T₁≤40° C.,

where n¹, n² are each independently an integer in the range of 4-3 000 000, especially 4-1 000 000, preferably 4-100 000, more preferably 4-10 000, even more preferably 4-5000,

where the repeat units of the chemical structure (I) within the polymer P¹ are the same or at least partly different from one another,

where the repeat units of the chemical structure (I) within the polymer P¹ are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

where the repeat units of the chemical structure (II) within the polymer P² are the same or at least partly different from one another,

where the repeat units of the chemical structure (II) within the polymer P² are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

and where, in the chemical structures (I) and (II), the R¹, R², R³, R⁴, R⁵ radicals are selected from the group consisting of hydrogen, branched or unbranched alkyl group having 1 to 4 carbon atoms, preferably R¹, R², R³, R⁴ methyl and R⁵ hydrogen or methyl,

X is selected from the group consisting of *—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, *—C°=CH—**,

where “*” in each case denotes the bond to the carbon atom joined to R¹ and R²,

where “**” in each case denotes the bond to the carbon atom joined to R³ and R⁴,

where “C′” denotes a carbon atom additionally joined to the Y radical,

where Y is selected from the bridging radicals (III) and (IV),

-   -   where (III) has the structure         &-(Y¹)_(p1)—[C═X¹]_(p2)—(Y²)_(p3)—B—(Y³)_(p6)—[C═X²]_(p5)—(Y⁴)_(p4)—&&,     -   and where (IV) has the structure         &-(Y⁵)_(p9)—(C═X³)_(p8)—(Y⁶)_(p7)-&&,     -   where, in the bridging radicals (III) and (IV),     -   p1, p2, p3 are each 0 or 1, with the proviso that it is not         simultaneously the case that p1=p3=1 and p2=0,     -   p4, p5, p6 are each 0 or 1, with the proviso that it is not         simultaneously the case that p4=p6=1 and p5=0,     -   p7, p8, p9 are each 0 or 1, with the proviso that it is not         simultaneously the case that p7=p9=1 and p8=0, and that, when         p7=1 and p8=0, p9=0,     -   X¹, X², X³, r, Y², Y³, Y⁴, Y⁵, Y⁶, are independently selected         from the group consisting of O, S,     -   B is a divalent, optionally substituted (hetero)aromatic radical         or a divalent, optionally substituted aliphatic radical, where         the optionally substituted aliphatic radical may additionally         have at least one group selected from ether, thioether, carbonyl         group, carboxylic ester group, sulphonic ester group, phosphoric         ester,

and where “&&” for Y denotes the bond via which Y is joined to X and where “&” for Y denotes the bond via which Y is joined to the carbon atom joined to R⁵.

3) In a preferred embodiment of the present invention, the invention relates to a process for preparing a polymer P¹ comprising n¹ repeat units of the general chemical structure (I)

which is characterized in that a polymer P² comprising n² repeat units of the general chemical structure (II)

is oxidized in a solvent comprising water and ethanol, where the ethanol is present in the solvent in deficiency relative to water, especially at a temperature T₁≤40° C.,

where n¹, n² are each independently an integer in the range of 4-3 000 000, especially 4-1 000 000, preferably 4-100 000, more preferably 4-10 000, even more preferably 4-5000,

where the repeat units of the chemical structure (I) within the polymer P¹ are the same or at least partly different from one another,

where the repeat units of the chemical structure (I) within the polymer P¹ are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

where the repeat units of the chemical structure (II) within the polymer P² are the same or at least partly different from one another,

where the repeat units of the chemical structure (II) within the polymer P² are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

and where, in the chemical structures (I) and (II), R¹═R²=R³═R⁴=methyl and R⁵=hydrogen or methyl,

X is selected from the group consisting of *—O—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, *—C′=CH—**,

where “*” in each case denotes the bond to the carbon atom joined to R¹ and R²,

where “**” in each case denotes the bond to the carbon atom joined to R³ and R⁴,

where “C′” denotes a carbon atom additionally joined to the Y radical,

where Y is selected from the bridging radicals (III) and (IV),

-   -   where (III) has the structure         &-(Y¹)_(p1)—[C═X¹]_(p2)—(Y²)_(p3)—B—(Y³)_(p6)—[C═X²]_(p5)—(Y⁴)_(p4).&&,     -   and where (IV) has the structure         ae(Y⁵)_(p9)—(C═X³)_(p8)—(Y⁵)_(p7)-&&,     -   where, in the bridging radicals (III) and (IV),     -   p1, p2, p3 are each 0 or 1, with the proviso that it is not         simultaneously the case that p1=p3=1 and p2=0,     -   p4, p5, p6 are each 0 or 1, with the proviso that it is not         simultaneously the case that p4=p6=1 and p5=0,     -   p7, p8, p9 are each 0 or 1, with the proviso that it is not         simultaneously the case that p7=p9=1 and p8=0, and that, when         p7=1 and p8=0, p9=0,     -   X¹, X², X³, Y¹, Y², Y³, Y⁴, Y⁵, Y⁶ are independently selected         from the group consisting of O, S,     -   B is a divalent (hetero)aromatic radical, preferably phenylene,         or a divalent aliphatic radical optionally substituted by at         least one group selected from —F, —Cl, —Br, —I, where the         optionally substituted aliphatic radical may additionally have         at least one group selected from ether, thioether,

and where “&&,” for Y denotes the bond via which Y is joined to X and where “&” for Y denotes the bond via which Y is joined to the carbon atom joined to R⁵.

4) In a more preferred embodiment of the present invention, the invention relates to a process for preparing a polymer P¹ comprising n¹ repeat units of the general chemical structure (I)

which is characterized in that a polymer P² comprising n² repeat units of the general chemical structure (II)

is oxidized in a solvent comprising water and ethanol, where the ethanol is present in the solvent in deficiency relative to water, especially at a temperature T₁≤40° C.,

where n¹, n² are each independently an integer in the range of 4-3 000 000, especially 4-1 000 000, preferably 4-100 000, more preferably 4-10 000, even more preferably 4-5000,

where the repeat units of the chemical structure (I) within the polymer P¹ are the same or at least partly different from one another,

where the repeat units of the chemical structure (I) within the polymer P¹ are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

where the repeat units of the chemical structure (II) within the polymer P² are the same or at least partly different from one another,

where the repeat units of the chemical structure (II) within the polymer P² are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in the adjacent repeat unit,

and where, in the chemical structures (I) and (II), R¹═R²=R²═R⁴=methyl and R⁵=hydrogen or methyl,

X is selected from the group consisting of *—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, *—C°=CH—**,

where “*” in each case denotes the bond to the carbon atom joined to R¹ and R²,

where “**” in each case denotes the bond to the carbon atom joined to R³ and R⁴,

where “C′” denotes a carbon atom additionally joined to the Y radical,

where Y is selected from the bridging radicals (ID) and (IV),

-   -   where (III) has the structure         &-(Y¹)_(p1)—[C═X¹]_(p2)—(Y²)_(p3)—B—(Y³)_(p6)[C═X²]_(p5)—(Y⁴)_(p4)—&&,     -   and where (IV) has the structure         &-(Y⁵)_(p9)—(C═X³)_(p8)—(Y⁵)_(p7)-&&,     -   where, in the bridging radicals (III) and (IV),     -   p1, p2, p3 are each 0 or 1, with the proviso that it is not         simultaneously the case that p1=p3=1 and p2=0,     -   p4, p5, p6 are each 0 or 1, with the proviso that it is not         simultaneously the case that p4=p6=1 and p5=0,     -   p7, p8, p9 are each 0 or 1, with the proviso that it is not         simultaneously the case that p7=p9=1 and p8=0, and that, when         p7=1 and p8=0, p9=0,     -   X¹=X²=X³=Y¹=Y²=Y³=Y⁴=Y⁵=Y⁵=O,     -   B is phenylene, or an alkylene radical which is optionally         substituted by at least one group selected from —F, —Cl, —Br, —I         and is preferably unsubstituted and preferably comprises 1 to 10         carbon atoms,

and where “&&” for Y denotes the bond via which Y is joined to X and where “&” for Y denotes the bond via which Y is joined to the carbon atom joined to R⁵.

In the embodiments described in points 1) to 4), X is selected from the group consisting of *—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, *—C′═CH—**.

When X=*—CH₂—C′H—CH₂—**, the general chemical structure (I) has the following structure of, and the general chemical structure (II) has the following structure (II)′:

where R¹, R², R³, R⁴, R⁵, Y have the definitions described in the respective embodiments.

When X=*—C′H—CH₂—**, the general chemical structure (I) has the following structure (I)″, and the general chemical structure (II) has the following structure (III)″:

where R¹, R², R³, R⁴, R⁵, Y have the definitions described in the respective embodiments.

When X=*—′═CH₂—**, the general chemical structure (I) has the following structure (II)′″, and the general chemical structure (II) has the following structure (II)′″:

where R¹, R², R³, R⁴, R⁵, Y have the definitions described in the respective embodiments.

It is particularly preferable here in accordance with the invention and especially in the embodiments cited in points 1) to 4) when X=*—CH₂—C′H—CH₂—**.

Most preferably, in the process according to the invention, the general chemical structure (I) has the following structure (I)″″, and the general chemical structure (II) has the following structure (II)″″:

where R⁵=methyl or hydrogen, preferably R⁵=methyl.

It will be apparent that the bridging radical (IV), when p7=p8=p9=0, may also be a direct bond.

It is a particular feature of the process according to the invention that it is performed at a temperature T₁≤40° C., preferably −25° C.≤T₁≤40° C., more preferably −20° C.≤T₁≤40° C., even more preferably −12° C.≤T₁≤30° C., even more preferably still 0° C.≤T₁≤25° C.

“Where the ethanol is present in the solvent in deficiency relative to water” means especially that the mass ratio of water to ethanol in the solvent is in the range of 51:49 to 99:1, preferably in the range of 1.1:1 to 98:2, more preferably in the range of 55:45 to 95:5, even more preferably in the range of 1.3:1 to 9:1, even more preferably still in the range of 4:1 to 8.5:1, most preferably in the range of 7.1:1 to 8.2:1.

It is further preferable that the proportion of the sum total of the weights of ethanol and water in the solvent is at least 50% by weight, more preferably at least 60% by weight, even more preferably at least 70% by weight, even more preferably at least 80% by weight, yet more preferably at least 90% by weight, even more preferably still at least 95% by weight, most preferably at least 99% by weight, based on the total weight of the solvent.

The solvent may, as well as water and ethanol, include further constituents, especially selected from the group consisting of halogenated hydrocarbons, aliphatic nitriles, aromatic nitriles, alcohols other than ethanol, aromatic hydrocarbons.

However, it is preferable that the proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent, more preferably of all C₁-C₁₀ alcohols other than ethanol in the solvent, is less than 50% by weight, based on the weight of the ethanol encompassed by the solvent.

It is more preferable that the proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent, more preferably of all C₁-C₁₀ alcohols other than ethanol in the solvent, is less than 25% by weight, based on the weight of the ethanol encompassed by the solvent.

It is even more preferable that the proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent, more preferably of all C₁-C₁₀ alcohols other than ethanol in the solvent, is less than 10% by weight, based on the weight of the ethanol encompassed by the solvent.

It is yet more preferable that the proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent, more preferably of all C₁-C₁₀ alcohols other than ethanol in the solvent, is less than 5% by weight, based on the weight of the ethanol encompassed by the solvent.

It is even more preferable still that the proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent, more preferably of all C₁-C₁₀ alcohols other than ethanol in the solvent, is less than 1% by weight, based on the weight of the ethanol encompassed by the solvent.

The solvent is especially used in such an amount that the weight of the solvent used is 1 to 5000 times, preferably 2.5 to 3000 times, more preferably 5 to 100 times and even more preferably 10-50 times the weight of the polymer P² used.

Oxidizing agents used may likewise be the oxidizing agents familiar to the person skilled in the art.

The oxidizing agent is especially selected from the group consisting of peroxides, metal compounds, air, preferably peroxides.

Peroxides are preferably selected from the group consisting of hydrogen peroxide, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, meta-chloroperbenzoic acid. The most preferred peroxide is hydrogen peroxide.

Metal compounds are preferably selected from the group consisting of silver oxide, lead tetraacetate, potassium hexacyanoferrate (III), potassium permanganate.

The reactant P² used in the process according to the invention can be obtained by prior art methods from commercially available chemicals, for example 2,2,6,6-tetramethyl-4-piperidinyl methacrylate. Such methods are described, for example, in EP 1 752 474 A1 or in European patent application 16172593.2. It is accordingly also additionally possible to use crosslinkers as well as the monomer in the synthesis of P². Suitable crosslinkers are compounds having more than one polymerizable group, the crosslinker preferably being selected from the group consisting of polyfunctional compounds based on (meth)acrylic acid, polyfunctional compounds based on allyl ether, polyfunctional compounds based on vinylic compounds. Polyfunctional compounds based on (meth)acrylic acid are particularly preferred.

Polyfunctional compounds based on (meth)acrylic acid are especially selected from ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propane-1,3-diol di(meth)acrylate, butane-2,3-diol di(meth)acrylate, butane-1,4-diol di(meth)acrylate, pentane-1,5-diol di(meth)acrylate, hexane-1,6-diol di(meth)acrylate, heptane-1,7-diol di(meth)acrylate, octane-1,8-diol di(meth)acrylate, nonane-1,9-diol di(meth)acrylate, decane-1,10-diol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerol di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate.

The oxidizing agent is especially used in such an amount that 1 to 40 mol, more preferably 1.5 to 15 mol, even more preferably 5 to 14.4 mol, yet more preferably 13 to 14 mol and most preferably 13 mol of the oxidizing agent are used per mole of NH group to be oxidized in the polymer P² used.

In the oxidation, it is additionally also possible to make use of a catalyst. The catalysts used in the nitroxylation are familiar to the person skilled in the art.

More particularly, nitroxylation can be accomplished using catalysts selected from compounds of the metals of the chromium group, especially molybdenum and tungsten. Preferably, the catalyst used for nitroxylation is a compound of tungsten.

Compounds of tungsten are especially selected from the group consisting of tungstic acid, tungstophosphoric acid, paratungstic acid, tungstates, tungstophosphates, paratungstates, tungsten oxides, tungsten carbonyls. Preferably, compounds of tungsten are selected in accordance with the invention from alkali metal salts and ammonium salts of the tungstates, more preferably from the group consisting of ammonium tungstate, sodium tungstate, potassium tungstate, even more preferably sodium tungstate.

Compounds of molybdenum are especially selected from the group consisting of molybdic acid, molybdophosphoric acid, paramolybdic acid, molybdates, molybdophosphates, paramolybdates, molybdenum oxides, molybdenum carbonyls. Preferably, compounds of molybdenum are selected in accordance with the invention from alkali metal salts and ammonium salts of the molybdates, more preferably from the group consisting of ammonium molybdate, sodium molybdate, potassium molybdate, molybdenum trioxide, molybdenum hexacarbonyl,

The catalyst is especially used in such an amount that 0.1 to 10 mol %, more preferably 1 to 5 mol %, even more preferably 2 to 3.5 mol % and even more preferably still 2.5 to 3.0 mol % of the catalyst is used per mole of the compound of the structure (I) used in step (a) of the process according to the invention.

The reaction time is likewise not particularly restricted, and is especially 1 to 100 hours, preferably 3 to 96 hours, even more preferably 10 to 96 hours, yet more preferably 25 to 96 hours, even more preferably still 72 to 96 hours, most preferably 90 to 96 hours.

The polymer P¹ obtained is then likewise isolated by methods familiar to the person skilled in the art, such as filtration and subsequent drying.

The end groups of the first repeat unit of the polymer P¹ which is present therefor in the chemical structure (I) at the bonds defined by “#”, and the end groups of the n¹th repeat unit of the polymer P¹ according to the invention which is present therefor in the chemical structure (I) at the bonds defined by “##”, are not particularly restricted and are a result of the polymerization method used in the method for preparing the polymer P¹. Thus, they may be termination fragments of an initiator or a repeat unit. Preferably, these end groups are selected from hydrogen, halogen, hydroxyl, unsubstituted aliphatic radical or aliphatic radical substituted by —ON, —OH, halogen (which may especially be an unsubstituted or correspondingly substituted alkyl group), (hetero)aromatic radical, which is preferably a phenyl radical, benzyl radical or α-hydroxybenzyl.

The end groups of the first repeat unit of the polymer P² which is present therefor in the chemical structure (II) at the bonds defined by “#”, and the end groups of the n²th repeat unit of the polymer P² according to the invention which is present therefor in the chemical structure (II) at the bonds defined by “##”, are not particularly restricted and are a result of the polymerization method used in the method for preparing the polymer P². Thus, they may be termination fragments of an initiator or a repeat unit. Preferably, these end groups are selected from hydrogen, halogen, hydroxyl, unsubstituted aliphatic radical or aliphatic radical substituted by —ON, —OH, halogen (which may especially be an unsubstituted or correspondingly substituted alkyl group), (hetero)aromatic radical, which is preferably a phenyl radical, benzyl radical or α-hydroxybenzyl.

Definitions

In the context of this invention, some terms are defined as follows:

“Nitroxyl” is a radical N O. function.

Nitroxylation is the oxidation of an NH group to a nitroxyl.

“At least partly different from one another” means, in the context of the invention, with regard to the polymer P¹, that at least two repeat units of the chemical structure (I) therein differ from one another, and more particularly means that at least two of the n mutually wined repeat units of the chemical structure (I) differ in at least one of the R¹, R², R³, R⁴, R⁵, X, Y radicals.

“At least partly different from one another” means, in the context of the invention, with regard to the polymer P², that at least two repeat units of the chemical structure (II) therein differ from one another, and more particularly means that at least two of the n mutually joined repeat units of the chemical structure (II) differ in at least one of the R¹, R², R³, R⁴, R⁵, X, Y radicals.

The “degree of oxidation” of the polymer P¹ (and if appropriate also of the polymer P²) means the proportion of nitroxyl groups, based on the sum total of all nitroxyl groups and non-nitroxylated secondary NH groups. It is determined in accordance with the invention by ESR. What is being determined here is how many N O functions are present in the molecule being examined in the particular case via the signal strength of the ESR signal measured based on the amount of the particular polymer used. The standard used in accordance with the invention is TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl). Via the determination of the number of N O. functions in the polymer P¹ and the comparison of the N O. functions in the polymer P² used, it is then possible to determine the degree of oxidation and hence the efficiency of the process according to the invention.

“Halogenated hydrocarbons” are preferably selected from the group consisting of dichloromethane, chloroform, dichloroethane. Aliphatic nitriles are preferably selected from the group consisting of acetonitrile, propionitrile, butyronitrile. Aromatic nitriles are preferably selected from the group consisting of benzonitrile, phenylacetonitrile. Alcohols other than ethanol are preferably selected from the group consisting of methanol, n-propanol, iso-propanol, n-butanol, sec-butanol, iso-butanol, tert-butanol, preferably methanol. Aromatic hydrocarbons are preferably selected from the group consisting of benzene, toluene.

“C₁-C₄ alcohols” in accordance with the invention are especially methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, iso-butanol, tart-butanol.

“C₁-C₁₀ alcohols” in accordance with the invention are especially methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, iso-butanol, tert-butanol and all alcohols having 5 to 10 carbon atoms.

“Substituted aliphatic radical” in the context of the invention especially means that, in the aliphatic radical in question, a hydrogen atom bonded to a carbon atom in the group in question is replaced by a group selected from (hetero)aromatic radical, —NO₂, —ON, —F, —Cl, —Br, —I, —C(═O)NR^(I)R^(II), —NR^(III)R^(IV), —C(═O)OR^(V), preferably —NO₂, —CN, —F, —Cl, —Br, —I, even more preferably —F, —Cl, —Br, —I, most preferably —F, —Cl, —Br, where R^(I), R^(II), R^(III), R^(IV), R^(V) are selected from H, alkyl, haloalkyl, aromatic, heteroaromatic, and where in the case that R^(Iv)=alkyl or haloalkyl may also be —O⁻.

An optionally substituted aliphatic radical is preferably unsubstituted.

An optionally substituted alkylene radical is preferably unsubstituted.

An alkylene radical having 1 to 10 carbon atoms especially has 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms and even more preferably 1 to 3 carbon atoms, and is most preferably methylene, ethylene or n-propylene.

An alkyl group having 1 to 10 carbon atoms especially has 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms and even more preferably 1 to 3 carbon atoms, and is most preferably methyl, ethyl or n-propyl.

A (hetero)aromatic radical in the context of the invention s a heteroaromatic or aromatic radical. A (hetero)aromatic radical may be monovalent, i.e. may be bonded to the rest of the molecule via just one of its carbon atoms (in the case of an aromatic radical) or via one of its carbon atoms or heteroatoms (in the case of a heteroaromatic radical).

A (hetero)aromatic radical may alternatively be divalent, i.e. may be bonded to the rest of the molecule via two of its carbon atoms (in the case of an aromatic radical) or may be bonded to the rest of the molecule via two of its carbon atoms, two of its heteroatoms or one of its carbon atoms and one of its heteroatoms (in the case of a heteroaromatic radical).

When they are not referred to explicitly as divalent in this invention, the term “(hetero)aromatic radical” in the context of the invention shall be understood to mean monovalent (hetero)aromatic radicals.

An aromatic radical has exclusively carbon atoms and at least one aromatic ring. An aromatic radical is especially selected from aryl radical, aralkyl radical, alkaryl radical. Aryl radicals have exclusively aromatic rings and are joined to the molecule via a carbon atom in the aromatic ring. An aryl radical is preferably phenyl.

Alkaryl radicals have at least one aromatic ring via which they are joined to the rest of the molecule and additionally also bear alkyl radicals on the aromatic ring. An alkaryl radical is preferably tolyl.

Aralkyl radicals are formally derived by replacement of a hydrocarbyl radical of an alkyl group with an aryl group or an alkaryl group. An alkaryl radical is preferably benzyl, phenylethyl, α-methylbenzyl.

A heteroaromatic radical is especially selected from heteroaryl radical, heteroaralkyl radical, alkylheteroaryl radical. It is an aromatic radical which additionally has at least one heteroatom, especially a heteroatom selected from the group consisting of nitrogen, oxygen, sulphur, within the aromatic ring or, in the case of a heteroaralkyl radical or of an alkylheteroaryl radical, alternatively or additionally outside the aromatic ring.

Preferred (hetero)aromatic radicals are selected from the group consisting of a ring of the above-defined chemical structure (III), azole, imidazole, pyrrole, pyrazole, triazole, tetrazole, thiophene, furan, thiazole, thiadiazole, oxazole, oxadiazole, pyridine, pyrimidine, triazine, tetrazine, thiazine, benzofuran, purine, indole, 9-anthryl, 9-phenanthryl.

A divalent (hetero)aromatic radical in the context of the invention is a divalent aromatic radical or a divalent heteroaromatic radical, preferably a divalent aromatic radical.

According to the invention, a divalent aromatic radical is a divalent hydrocarbyl group having at least 6 and preferably 6 to 30 carbon atoms, of which at least 6 carbon atoms are present in an aromatic system and the other carbon atoms, if present, are saturated. The divalent aromatic radical may be joined to the rest of the molecule via carbon atoms in the aromatic system or, if present, saturated carbon atoms.

Preferably, a divalent aromatic radical is a chemical structure (d)

where y′ is an integer >0, preferably from 0 to 24; where y″ is an integer >0, preferably from 0 to 24; and where preferably, at the same time, y′ ¢ y″≤24.

A divalent heteroaromatic radical is a divalent aromatic radical which additionally has at least one heteroatom, especially at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulphur, within or outside the aromatic ring, preferably within the aromatic ring, but is especially joined to the rest of the molecule via carbon atoms.

“Optionally substituted (hetero)aromatic radical” especially denotes unsubstituted (hetero)aromatic radical and preferably unsubstituted aromatic radical.

“Substituted or unsubstituted (hetero)aromatic radical” especially denotes unsubstituted (hetero)aromatic radical and preferably unsubstituted aromatic radical.

“Substituted (hetero)aromatic radical” in the context of the invention especially means that, in the (hetero)aromatic radical in question, a hydrogen atom bonded to a carbon atom in the group in question is replaced by a group selected from alkyl group, alkenyl group, alkynyl group, haloalkyl group, —NO₂, —ON, —F, —Cl, —Br, —C(═O)NR^(I)R^(II), —NR^(III)R^(V), preferably —NO₂, —ON, —F, —Cl, alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, where R^(I), R^(II), R^(III), R^(V) are selected from H, alkyl group having preferably 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, haloalkyl group having preferably 1 to 10 carbon atoms, aromatic, heteroaromatic, and where R^(III) in the case that R^(V)=alkyl or haloalkyl may also be —O⁻.

“Where the optionally substituted aliphatic radical may additionally have at least one group selected from ether, thioether, optionally nitroxylated amino ether, carbonyl group, carboxylic ester group, carboxamide group, sulphonic ester group, phosphoric ester” means:

In the case of ether, that an —O— group is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of thioether, that an —S— group is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the optionally nitroxylated amino ether, that an —NR′— with R′═H, —O. group or alkyl having 1 to 10 carbon atoms, preferably R′═H or alkyl having 1 to 10 carbon atoms, is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the carbonyl group, that a —C(═O)— group is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the carboxylic ester group, that a —C(═O)—O— group is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the carboxamide group, that a —C(═O)—NU— group with U═H or alkyl having 1 to 10 carbon atoms is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the sulphonic ester group, that an —S(O)₂O— group is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In the case of the phosphoric ester group, that a group selected from −OP(═O)(O⁻(W^(d+))_(1/z))−O—, —OP(═O)(OR″)—O— where R″═H or alkyl group having 1 to 10 carbon atoms is present in the optionally substituted aliphatic radical at least between two sp³-hybridized carbon atoms of the aliphatic radical, preferably between two —CH₂— groups of the aliphatic radical, even more preferably between two —CH₂CH₂— groups of the aliphatic radical.

In this case, W^(d+) is selected from the group consisting of alkali metal cation, where the alkali metal cation is preferably selected from the group consisting of Li⁺, Na⁺, K⁺, alkaline earth metal cation, where the alkaline earth metal cation is preferably selected from the group consisting of Mg²⁺, Ca²⁺, transition metal cation, where the transition metal cation is preferably selected from the group consisting of iron cation, zinc cation, mercury cation, nickel cation, cadmium cation, and from tetraalkylammonium cation, imidazolium cation, monoalkylimidazolium cation, dialkylirnidazolium cation, where the alkyl groups in the tetraalkylammonium cation, rnonoalkylimidazolium cation, dialkylimidazolium cation each independently preferably have 1 to 30 carbon atoms. Moreover, d indicates the number of positive charges of W^(d+).

Preferably, W^(d+) is selected from the group consisting of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Fe²⁺, Fe³⁺. Cd²⁺, Hg⁺, Hg²⁺, Ni²⁺, Ni³⁺, Ni⁴⁺,

where d in the case of each of Li⁺, Na⁺, K⁺, Hg⁺=1,

where d in the case of each of Mg²⁺, Ca²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Fe²⁺=2,

where d in the case of Fe³⁺, Ni³⁺=3,

where d in the case of Ni⁴⁺=4.

Fields of Use of the Polymer P¹ Prepared by the Process According to the Invention

The polymer P¹ is especially suitable for use as redox-active electrode material in an electrical charge storage means, preferably for storage of electrical energy, and more preferably as a positive electrode element.

More preferably, the redox-active electrode material takes the form of an at least partial surface coating of electrode elements for electrical charge storage means, especially secondary batteries. Electrode elements here comprise at least one surface layer and one substrate.

A redox-active material for storage at electrical energy is a material which can store electrical charge and release it again, for example by accepting and releasing electrons. This material can be used, for example, as an active electrode material in an electrical charge storage means. Such electrical charge storage means for storage of electrical energy are especially selected from the group consisting of secondary batteries (also called “accumulators”), redox flow batteries, supercapacitors, and are preferably secondary batteries.

Preferably, the electrical charge storage means is a secondary battery. A secondary battery comprises a negative electrode and a positive electrode which are separated from one another by a separator, and an electrolyte which surrounds the electrodes and the separator.

The separator is a porous layer which is ion-permeable and enables the balancing of the charge. The task of the separator is to separate the positive electrode from the negative electrode and to enable balancing of charge through permutation of ions. The separator used in the secondary battery is especially a porous material, preferably a membrane consisting of a polymeric compound, for example polyolefin, polyamide or polyester. In addition, it is possible to use separators made from porous ceramic materials.

The main task of the electrolyte is to assure ion conductivity, which is needed to balance the charge. The electrolyte of the secondary battery may be either a liquid or an oligomeric or polymeric compound having high ion conductivity (“gel electrolyte” or “solid state electrolyte”). Preference is given, however, to an oligomeric or polymeric compound.

If the electrolyte is liquid, it is especially composed of one or more solvents and one or more conductive salts.

The solvent of the electrolytes preferably independently comprises one or more solvents having a high boiling point and high ion conductivity but low viscosity, for example acetonitrile, dimethyl sulphoxide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, diglyme, triglyme, tetraglyme, ethyl acetate, 1,3-dioxolane or water.

The conductive salt in the electrolyte consists of a cation of the formula Me^(e+) and an anion of the formula An^(f−) in the formula (M^(e+))_(a)(An^(f−))_(b) where e and f are integers depending on the charge of M and An; a and b are integers which represent the molecular composition of the conductive salt. Cations used in the abovementioned conductive salt are positively charged ions, preferably metals of the first and second main groups, for example lithium, sodium, potassium or magnesium, but also other metals of the transition groups, such as zinc, and organic cations, for example quaternary ammonium compounds such as tetraalkylammonium compounds. The preferred cation is lithium.

Anions used in said conductive salt are preferably inorganic anions such as hexafluorophosphate, tetrafluoroborate, triflate, hexafluoroarsenate, hexafluoroantimonate, tetrafluoroaluminate, tetrafluoroindate, perchlorate, bis(oxalato)borate, tetrachloroaluminate, tetrachlorogallate, but also organic anions, for example N(CF₃SO₂)₂ ⁻ , CF₃SO₃ ⁻ , alkoxides, for example tert-butoxide or iso-propoxide, but also halides such as fluoride, chloride, bromide and iodide. The preferred anion is perchlorate, ClO₄ ⁻ .

The preferred conductive salt is thus LiClO₄.

If ionic liquids are used, they can be used either as solvent of the electrolyte, as conductive salt, or else as complete electrolyte.

In the embodiment in which the redox-active electrode material takes the form of an at least partial surface coating of electrode elements for electrical charge storage means, especially secondary batteries, an electrode element has an at least partial layer on a substrate surface. This layer especially comprises a composition comprising the polymer according to the invention as redox-active material for charge storage and especially at least also a conductivity additive and especially also at least one binder additive.

The application of this composition (another expression for composition: “composite”) on the substrate is possible by means of methods known to those skilled in the art. More particularly, the polymer according to the invention is applied on the substrate with the aid of an electrode slurry. The substrate of the electrode element is especially selected from conductive materials, preferably metals, carbon materials, oxide substances.

Preferred metals are selected from platinum, gold, iron, copper, aluminium or a combination of these metals. Preferred carbon materials are selected from glassy carbon, graphite film, graphene, carbon sheets. Preferred oxide substances are, for example, selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), antimony zinc oxide (AZO), fluorine tin oxide (FTO) or antimony tin oxide (ATO).

The surface layer of the electrode element comprises at least the polymer according to the invention as redox-active material for charge storage and especially at least a conductivity additive and a binder additive.

The conductivity additive is especially at least one electrically conductive material, preferably selected from the group consisting of carbon materials, electrically conductive polymers, and especially carbon materials. Carbon materials are especially selected from the group consisting of carbon platelets, carbon fibres, carbon nanotubes, graphite, carbon black, graphene, and are more preferably carbon fibres. Electrically conductive polymers are especially selected from the group consisting of polyanilines, polythiophenes, polyacetylenes, poly(3,4-ethylenedioxythiophene) polystyrenesulphonate (=PEDOT:PSS), polyarcenes.

Binder additives are especially materials having binder properties and are preferably polymers selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyvinyl chloride, polycarbonate, polystyrene, polyacrylates, polymethacrylates, polysulphones, cellulose derivatives, polyurethanes.

The polymer P² is especially applied to the substrate of the electrode element in an electrode slurry.

The electrode slurry is a solution or suspension and comprises the polymer according to the invention and especially the above-described conductivity additive and the above-described binder additive.

The electrode slurry preferably comprises a solvent and further constituents comprising redox-active material for storage of electrical energy (which is especially the polymer according to the invention), and preferably also the conductivity additive and the binder additive.

In the further constituents, preferably, the proportion of the redox-active material for storage of electrical energy (which is especially the polymer according to the invention) is from 5 to 100 percent by weight, the proportion of the conductivity additive from 0 to 80 and preferably 5 to 80 percent by weight, and the proportion of binder additive from 0 to 10 and preferably 1 to 10 percent by weight, where the sum total is 100 percent by weight.

Solvents used for the electrode slurry are independently one or more solvents, preferably solvents having a high boiling point, more preferably selected from the group consisting of N-methyl-2-pyrrolidone, water, dimethyl sulphoxide, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, α-butyrolactone, tetrahydrofuran, dioxolane, sulpholane, N,N′-dimethylformamide, N,N′-dimethylacetarnide. The concentration of the redox-active material, especially of the polymer according to the invention for storage of electrical energy in the above mentioned electrode slurry is preferably between 0.1 and 10 mg/ml, more preferably between 0.5 and 5 mg/ml.

If the polymer of this invention as redox-active material is used as positive electrode element for electrical charge storage means, the redox-active material used for electrical charge storage in the negative electrode is a material which exhibits a redox reaction at a lower electrochemical potential than the polymer of this invention. Preference is given to those materials selected from the group consisting of carbon materials, which are especially selected from the group consisting of graphite, graphene, carbon black, carbon fibres, carbon nanotubes, metals or alloys, which are especially selected from the group consisting of lithium, sodium, magnesium, lithium-aluminium, Li—Si, Li—Sn, Li—Ti, Si, SiO, SiO₂, Si—SiO₂ complex, Zn, Sn, SnO, SnO₂, PbO, PbO₂, GeO, GeO₂, WO₂, MoO₂, Fe₂O₃, Nb₂O₅, TiO₂, Li₄Ti₅O₁₂, and Li₂Ti₃O₇, and organic redox-active materials. Examples of organic redox-active materials are compounds having a stable organic radical, compounds having an organosulphur unit, having a quinone structure, compounds having a dione system, conjugated carboxylic acids and salts thereof, compounds having a phthalimide or naphthalimide structure, compounds having a disulphide bond and compounds having a phenanthrene structure and derivatives thereof. If an abovementioned redox-active oligomeric or polymeric compound is used in the negative electrode, this compound may also be a composite, i.e, a composition, consisting of this oligomeric or polymeric compound, a conductivity additive and a binder additive in any ratio. The conductivity additive in this case too is especially at least one electrically conductive material, preferably selected from the group consisting of carbon materials, electrically conductive polymers, and especially carbon materials. Carbon materials are especially selected from the group consisting of carbon fibres, carbon nanotubes, graphite, carbon black, graphene, and are more preferably carbon fibres. Electrically conductive polymers are especially selected from the group consisting of polyanilines, polythiophenes, polyacetylenes, poly(3,4-ethylenedioxythiophene) polystyrenesulphonate “PEDOT:PSS”), polyarcenes. Binder additives in this case too are especially materials having binder properties and are preferably polymers selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropyiene, polyvinyl chloride, polycarbonate, polystyrene, polyacrylates, polymethacrylates, polysulphones, cellulose derivatives, polyurethanes.

This composite may, as described above, be present as a layer on a substrate through a known film-forming process with the aid of an electrode slurry.

The examples which follow are intended to further elucidate the invention, but without restricting it thereto.

EXAMPLES

I. Chemicals Used

2,2,6,6-Tetramethyl-4-piperidinyl methacrylate (CAS number: 31582-45-3; melting point 61° C., abbreviated hereinafter as “TAA-of-MA”) was synthesized by prior art methods.

Ethylene glycol dimethacrylate (CAS number: 97-90-5) was obtained from Evonik.

Ammonium peroxodisulphate (CAS number: 7727-54-0) was obtained from Sigma Aldrich.

Polyoxyethylene nonylphenyl ether (CAS number: 68412-54-4) was obtained from Sigma Aldrich.

Sodium dodecylbenzenesulphonate (CAS number: 25155-30-0) was obtained from Sigma Aldrich.

4,4′-Azobis(4-cyanovaleric acid) (CAS number: 2638-94-0) was obtained from Wako V-501 # AWL2803.

Sodium tungstate dihydrate (CAS number: 10213-10-2) was obtained from Sigma Aldrich.

Ethylenediaminetetraacetic acid (abbreviated hereinafter as “EDTA”; CAS number: 60-00-4) was obtained from Roth.

TEMPO (2,2,6,6,-Tetramethylpiperidinyl-N-oxyl; CAS number: 2564-83-2) was obtained from Sigma-Aldrich.

II. Polymerization of TAA-ol to poly(2.2.6,6-tetramethylpiperidinyloxylmethacrylate) 1

150.0 g of TAA-ol-MA (melting point 61° C.), 1 g of a mixture of 2 parts sodium dodecylbenzenesulphonate and 1 part polyoxyethylene nonylphenyl ether and 2.7 g of ethylene glycol dimethacrylate were added to 467 ml of water in a 1 I jacketed reactor with stirrer and condenser, and heated to 65° C., Thereafter, the mixture was dispersed at 6000 rpm for 15 min with an Ultraturrax (machine: Ultra-Turrax T series disperser; from IKA-Werke GmbH and Co. KG; model: T 25 D; dispersion tool: S 25 N-25 G) and then while cooling to 40° C. over 30 minutes.

The dispersion thus obtained was transferred into a reactor, and equilibrated further therein to 40° C. The dispersion was placed under a nitrogen blanket and the passage of nitrogen was continued during the reaction that followed. Thereafter, 0.27 g of ammonium peroxodisulphate was added and the mixture was stirred overnight at a temperature between 40° C. and 45° C. To complete the reaction, the mixture was then polymerized at 65° C. for another 1 hour. Then the solution was cooled to room temperature.

The quantitative yield of polymer 1 corresponded to 90%, The polymer 1 was in the form of a finely distributed precipitate in the reactor and could be filtered and isolated without any problem.

III. Comparative Experiments C₁ to C₆ and Inventive Experiments I1 to I3: Oxidation of 1 to poly(2.2.6,6-tetramethylpiperidinyloxylmethacrylate) 2

40 g of polymer 1 obtained as described in section II were converted to a slurry in a flask with 20 g of water. The temperature of the flask was adjusted by means of a water bath or ice bath to room temperature (=25° C.; C2, C4, C5, C6) or 1° C. (C1, C3, 11, 13). While stirring with a stirrer motor, 80 g of water (C1, C2), of a mixture of water with methanol (C3, C4), of ethanol (C5, C6), or of a mixture of water with ethanol (I1, I2, I3), were then added. In the case of comparative experiments C5 and C6, for establishment of the desired ratio of ethanol and water, the corresponding proportion of the water used to form the slurry was removed prior to addition of the ethanol. In the case of comparative experiment C3 and of inventive experiments I1 and I3, after addition of the alcoholic solution, the suspension obtained was cooled to 0° C. (C3, I1) or with a coolant mixture to ˜−12° C. (I3). The suspension thus obtained was then stirred for a further 30 minutes, in order to allow the polymer to swell.

This was followed by the addition of 1.76 g of sodium tungstate dihydrate and 0.45 g of EDTA. After ˜1 minute, for oxidation, firstly 27.2 g of 30% aqueous hydrogen peroxide solution was then added in portions, followed after a further half an hour by 27.2 g of 50% aqueous hydrogen peroxide solution. The mixture was then stirred at the temperature T₁ specified in the table in section V for 90 hours and, toward the end, heated to 40° C. for another 1 hour in each case.

Thereafter, the reaction mixture was cooled, filtered through a fluted filter, washed three times with 50 g of water and then put in a vacuum drying cabinet overnight. The completeness of the oxidation (degree of oxidation=proportion of secondary NH groups that have been oxidized to N ©) was determined by means of ESR.

IV. ESR Analysis

Electron spin resonance spectra were recorded by means of a spin EMXmicro CW-EPR spectrometer (EMX micro EMM-6/1/9-VT control unit, ER 070 magnet, EMX premium ER04 X-band microwave bridge, equipped with a EMX standard resonator, EMX080 power unit) from Bruker Corporation. The samples were analysed at room temperature and quantitatively evaluated with the Bruker Xenon software package, version 1.1 b86. The SpinCount™ software module. The spectrometer was calibrated with TEMPO (99% purity, Sigma-Aldrich Chemie GmbH) as reference. No internal reference was present during the sample measurement. Three samples were analysed for each substance.

V. Results

The following table states the ratio of water and methanol/ethanol that was present in the solution during the oxidation, what temperature was utilized in the oxidation and how high the degree of oxidation determined by means of ESR was:

Solvents used Ratio of Temperature Degree of Experiment H₂O Methanol Ethanol water:alcohol T₁ oxidation C1 x — — — 1° C. 81% C2 x — — — 25° C. 96% C3 x x — 7.1:1 0° C. 88% C4 x x — 7.1:1 25° C. 96% C5 x x 0.75:1  25° C. 96.6%  C6 x x 0.75:1  25° C. 95.2%  I1 x — x 7.1:1 0° C. 98% I2 x — x 7.1:1 25° C. 98% I3 x — x 1.1:1 ~−12° C. 98.4% 

VI. Results

As apparent from the table shown in point V, a better degree of oxidation is achieved when a mixture of ethanol and water is used compared to water (C1, C2) or a mixture of water with methanol (C3, C4). However, this effect was observed only for those solvents in which ethanol is present in deficiency in relation to water, as apparent from the comparison of comparative examples C5 and C6 with inventive examples I1, I2 and I3.

The degree of oxidation of 98% or 98.4% observed in inventive examples I1, I2 and I3 is higher than that described in the prior art (page 8 line 33 of EP 1 911 775 A1 describes a conversion efficiency of 95.5%).

This result, namely that such a high degree of oxidation can be observed in an aqueous solvent containing ethanol in deficiency relative to water, is completely surprising. 

1: A process for preparing a polymer P¹ comprising n¹ repeat units of a chemical structure (I)

said process comprising: oxidizing a polymer P² comprising n² repeat units of a chemical structure (II)

in a solvent comprising water and ethanol, wherein the ethanol is present in the solvent in deficiency relative to water, wherein n¹, n² are each independently an integer in a range of 4-3 000 000, wherein the repeat units of the chemical structure (I) within the polymer P¹ are the same or at least partly different from one another, wherein the repeat units of the chemical structure (I) within the polymer P¹ are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in an adjacent repeat unit, wherein the repeat units of the chemical structure (II) within the polymer P² are the same or at least partly different from one another, wherein the repeat units of the chemical structure (II) within the polymer P² are joined to one another in such a way that the bond identified by “#” in a particular repeat unit is joined to the bond identified by “##” in an adjacent repeat unit, and wherein, in the chemical structures (I) and (II), the R¹, R², R³, R⁴, R⁵ radicals are each independently selected from the group consisting of hydrogen, branched alkyl group having 1 to 4 carbon atoms and unbranched alkyl group having 1 to 4 carbon atoms, X is selected from the group consisting of *—CH₂—C′H—CH₂—**, *—C′H—CH₂—**, and *—C′═CH—**, wherein “*” in each case denotes the bond to the carbon atom joined to R¹ and R², “**” in each case denotes the bond to the carbon atom joined to R³ and R⁴, “C” denotes a carbon atom additionally joined to the Y radical, Y is selected from the bridging radicals (III) and (IV), wherein (III) has a structure &-(Y¹)_(p1)—[C═X¹]_(p2)—(Y²)_(p3)—B—(Y³)_(p6)—[C═X²]_(p5)—(Y⁴)_(p4)—&&, and wherein (IV) has a structure &-(Y⁵)_(p9)—(C═X³)_(p8)—(Y⁶)_(p7)-&&, wherein, in the bridging radicals (III) and (IV),  p1, p2, p3 are each 0 or 1, with the proviso that it is not simultaneously the case that p1=p3=1 and p2=0,  p4, p5, p6 are each 0 or 1, with the proviso that it is not simultaneously the case that p1=p6=1 and p5=0,  p7, p8, p9 are each 0 or 1, with the proviso that it is not simultaneously the case that p7=p9=1 and p8=0, and that, when p7=1 and p8=0, p9=0,  X¹, X², X³ are independently selected from the group consisting of O, and S,  Y¹, Y², Y³, Y⁴, Y⁵, Y⁶ are independently selected from the group consisting of O, S, NH, and N-alkyl, and  Y¹, when p1=1, p2=p3=0, may also be N O.,  Y⁴, when p4=1, p5=p6=0, may also be N O.,  Y⁵, when p9=1, p7=p8=0, may also be N O.,  B is a divalent, optionally substituted (hetero)aromatic radical or a divalent, optionally substituted aliphatic radical, wherein the optionally substituted aliphatic radical may additionally have at least one group selected from the group consisting of ether, thioether, optionally nitroxylated amino ether, carbonyl group, carboxylic ester group, carboxamide group, sulphonic ester group, and phosphoric ester,  “&&” for Y denotes the bond via which Y is joined to X “&” for Y denotes the bond via which Y is joined to the carbon atom joined to R. 2: The process according to claim 1, wherein X¹, X², X³, Y¹, Y², Y³, Y⁴, Y⁵, Y⁶ are independently selected from the group consisting of O, and S, wherein B is a divalent, optionally substituted (hetero)aromatic radical or a divalent, optionally substituted aliphatic radical, and wherein the optionally substituted aliphatic radical may additionally have at least one group selected from the group consisting of ether, thioether, carbonyl group, carboxylic ester group, sulphonic ester group, and phosphoric ester. 3: The process according to claim 2, wherein R¹═R²═R³═R⁴=methyl and R⁵=hydrogen or methyl, wherein B is a divalent (hetero)aromatic radical or a divalent aliphatic radical optionally substituted by a group selected from the group consisting of —F, —Cl, —Br, and —I, wherein the optionally substituted aliphatic radical may additionally have at least one group selected from the group consisting of ether, and thioether. 4: The process according to claim 3, wherein X¹=X²=X³=Y¹=Y²=Y³=Y⁴=Y⁵=Y⁶=O, phenylene or an alkylene radical optionally substituted by at least one group selected from the group consisting of —F, —Cl, —Br, and —I. 5: The process according to claim 1, wherein X=*—CH₂—C′H—CH₂—**. 6: The process according to claim 5, wherein the chemical structure (I) has the following structure (II)″″, and the chemical structure (II) has the following structure (II)″″:

wherein R⁵=methyl or hydrogen. 7: The process according to claim 1, which is conducted at a temperature T₁≤40° C. 8: The process according to claim 1, wherein a mass ratio of water to ethanol in the solvent is in a range of 51:49 to 99:1. 9: The process according to claim 1, wherein a proportion of a sum total of the weights of ethanol and water in the solvent is at least 50% by weight, based on a total weight of the solvent. 10: The process according to claim 8, wherein a proportion by weight of all C₁-C₄ alcohols other than ethanol in the solvent is less than 50% by weight, based on the weight of the ethanol encompassed by the solvent. 11: The process according to claim 1, wherein n¹, n² are each independently an integer in a range of 4-1 000
 000. 